350 On some Combinations of Plaiina. 



side, occasioned by the of>eration of light, or the partial 

 pressure of a body in contact, appeared, in every case 

 which has come under my observation, the obvious cause 

 of the motions of tendrils ; and therefore, in conformity 

 with the conclusions I drew in my last memoir, respecting 

 the growth of roots, I shall venture to infer, that they are 

 the result of pure necessity only, uninfluenced by any de- 

 grees of sensation, or intellectual powers, 

 I am, my dear sir. 



With much regard, &c. 



Downton, April 27, 1812. Tho. AnDREW KnIGHT. 



LXIII. On some Comhivations of Platina. By Edmund 

 Davy, Esq., of the Royal Institution. Communicated 

 ly the Author. 



[Continued from page 278.] 



W HtLST that part of my paper in the Philosophical Maga- 

 zine for November was printing, I obtained some new 

 combinations of platina. My leisure hours since this 

 period have been devoted to the examination of these sub- 

 stances, yet the time has been by no means sufficient to 

 enable me to complete the investigation. I could wish to 

 have made some experiments which were connected with 

 the subject, and to have repeated others on a larger scale. 

 As, however, the facts I have to relate, are for the most 

 part new, no apology, I trust, will be necessary for 

 brmging them forward in what may be considered an 

 imperfect state. 



The order in which the details will be made, connected 

 with the examination of these compounds, is of little 

 importance: as an acquaintance with the sulphate of 

 platina must necessarily precede the knowledge of the other 

 combinations, it would seem proper first to describe this 

 substance. 



Of Sulphate of Platina. 



Sulphate of platina appears to have been first slightly 

 noticed by M. Proust* in a letter to M. Vauquelin j but 

 it has not 1 believe been hitherto examined. 



I have obtained it by the agency of strong nitrous acid 

 on the hydrosulphurel of platina previously washed, and in 

 a moist state. The experiment may be easily made in a 



• Annales rfe Chimie, tome xlix. 



florence 



